X-linked Inheritance

Genes are the blueprints for making proteins. These are the substances our bodies
need to form and work well. Most genes come in pairs, one of which is inherited from
the mother and the other from the father. A mutation is a change in a gene that keeps
it from working right. Mutations in genes are inherited from our biological parents
in certain ways. One of the common patterns of genetic inheritance is called X-linked
inheritance.

What is X-linked inheritance?

X-linked inheritance means that the gene change (alteration or mutation) causing the
trait or the disorder is located on the X chromosome. Females have 2 X chromosomes,
while males have 1 X and 1 Y chromosome.

Mutations in genes on the X chromosome can be recessive or dominant. Their expression
in females and males isn’t the same. This is because the genes on the Y chromosome
don’t exactly pair up with the genes on the X chromosome, like they do in females. In
most cases, X-linked recessive mutations happen in females only when they have 2 copies
of the mutation (1 on each X chromosome). However, for males, if their only copy of
the X chromosome has a mutation, then they will have the disorder.

Note that, to date, there haven’t been any genes linked to cancer found on the X chromosome.
However, studies of families with a strong history of prostate cancer have found some
evidence for a prostate cancer gene on this chromosome.